The exo-β-N-acetylmuramidase NamZ from Bacillus subtilis is the founding member of a family of exo-lytic peptidoglycan hexosaminidases

Endo-β-N-acetylmuramidases, commonly known as lysozymes, are well-characterized antimicrobial enzymes that catalyze an endo-lytic cleavage of peptidoglycan; i.e., they hydrolyze the β-1,4-glycosidic bonds connecting N-acetylmuramic acid (MurNAc) and N-acetylglucosamine (GlcNAc). In contrast, little is known about exo-β-N-acetylmuramidases, which catalyze an exo-lytic cleavage of β-1,4-MurNAc entities from the non-reducing ends of peptidoglycan chains. Such an enzyme was identified earlier in the bacterium Bacillus subtilis, but the corresponding gene has remained unknown so far. We now report that ybbC of B. subtilis, renamed namZ, encodes the reported exo-β-N-acetylmuramidase. A ΔnamZ mutant accumulated specific cell wall fragments and showed growth defects under starvation conditions, indicating a role of NamZ in cell wall turnover and recycling. Recombinant NamZ protein specifically hydrolyzed the artificial substrate para-nitrophenyl β-MurNAc and the peptidoglycan-derived disaccharide MurNAc-β-1,4-GlcNAc. Together with the exo-β-N-acetylglucosaminidase NagZ and the exo-muramoyl-l-alanine amidase AmiE, NamZ degraded intact peptidoglycan by sequential hydrolysis from the non-reducing ends. A structure model of NamZ, built on the basis of two crystal structures of putative orthologs from Bacteroides fragilis, revealed a two-domain structure including a Rossmann-fold-like domain that constitutes a unique glycosidase fold. Thus, NamZ, a member of the DUF1343 protein family of unknown function, is now classified as the founding member of a new family of glycosidases (CAZy GH171; www.cazy.org/GH171.html). NamZ-like peptidoglycan hexosaminidases are mainly present in the phylum Bacteroidetes and less frequently found in individual genomes within Firmicutes (Bacilli, Clostridia), Actinobacteria, and γ-proteobacteria.

Temperature-Dependent Spin Transport and Current-Induced Torques in Superconductor-Ferromagnet Heterostructures

We investigate the injection of quasiparticle spin currents into a superconductor via spin pumping from an adjacent ferromagnetic metal layer. To this end, we use NbN-Ni_{80}Fe_{20}(Py) heterostructures with a Pt spin sink layer and excite ferromagnetic resonance in the Permalloy layer by placing the samples onto a coplanar waveguide. A phase sensitive detection of the microwave transmission signal is used to quantitatively extract the inductive coupling strength between the sample and the coplanar waveguide, interpreted in terms of inverse current-induced torques, in our heterostructures as a function of temperature. Below the superconducting transition temperature T_{c}, we observe a suppression of the dampinglike torque generated in the Pt layer by the inverse spin Hall effect, which can be understood by the changes in spin current transport in the superconducting NbN layer. Moreover, below T_{c} we find a large fieldlike current-induced torque.

How does curvature affect the free-energy barrier of stalk formation? Small vesicles vs apposing, planar membranes

Using molecular simulations of POPC lipids in conjunction with the calculation of the Minimum Free-Energy Path (MFEP), we study the effect of strong membrane curvature on the formation of the first fusion intermediate—the stalk between a vesicle and its periodic image. We find that the thermodynamic stability of this hourglass-shaped, hydrophobic connection between two vesicles is largely increased by the strong curvature of small vesicles, whereas the intrinsic barrier to form a stalk, i.e., associated with dimple formation and lipid tails protrusions, is similar to the case of two, apposing, planar membranes. A significant reduction of the barrier of stalk formation, however, stems from the lower dehydration free energy that is required to bring highly curved vesicle into a distance, at which stalk formation may occur, compared to the case of apposing, planar membranes.

Micro- and macrovascular function in patients suffering from primary adrenal insufficiency: a cross-sectional case-control study

BACKGROUND

Despite adequate glucocorticoid (GC) and mineralocorticoid (MC) replacement therapy, patients suffering from primary adrenal insufficiency (AI) have an increased mortality, mainly due to cardiovascular diseases. Only little knowledge exists on the contribution of MC substitution to the cardiovascular risk. Therefore, this study investigates the impact of plasma renin concentration on parameters of micro- and macrovascular function.

METHODS

26 patients with primary AI [female = 18, age: 51 (28; 78) years; BMI: 24 (18; 40) kg/m²; disease duration: 18 (5; 36) years] were included in this cross-sectional analysis. Intima media thickness (IMT) and pulse wave velocity (PWV) were investigated to assess macrovascular remodeling and arterial stiffness. Microvascular function was estimated by post-occlusive reactive hyperemia using laser Doppler fluxmetry. Baseline perfusion, biological zero, peak perfusion, time to peak and recovery time were recorded. Patients were grouped according to their median plasma renin concentration of previous visits (Renin_high vs Renin_low) and were compared to a group of healthy women [age: 44 (43; 46) years; BMI: 24.2 (21.8; 27.5)].

RESULTS

PWV was significantly higher in AI patients compared to controls [9.9 (5; 18.5) vs 7.3 (6.8; 7.7) m/s; p < .01], whereas no differences in microvascular function could be found. In Renin_low time to peak perfusion was significantly longer [6.0 (3; 15) vs 3.5 (1.5; 11) s; p < .05], whereas no differences in IMT and PWV were observed between Renin_high and Renin_low. No impact of GC dose was observed.

CONCLUSIONS

Microvascular function is not impaired in patients with primary AI under adequate replacement therapy, although higher renin concentrations are associated with subclinical improvements. No relation between RAAS activity and macrovascular function is observed, while arterial stiffness might be increased in primary AI.

Decreased angiogenesis as a possible pathomechanism in cervical degenerative myelopathy

Endogenous immune mediated reactions of inflammation and angiogenesis are components of the spinal cord injury in patients with degenerative cervical myelopathy (DCM). The aim of this study was to identify alteration of certain mediators participating in angiogenetic and inflammatory reactions in patients with DCM. A consecutive series of 42 patients with DCM and indication for surgical decompression were enrolled for the study. 28 DCM patients were included, as CSF samples were taken preoperatively. We enrolled 42 patients requiring surgery for a thoracic abdominal aortic aneurysm (TAAA) as neurologically healthy controls. In 38 TAAA patients, CSF samples were taken prior to surgery and thus included. We evaluated the neurological status of patients and controls prior to surgery including NDI and mJOA. Protein-concentrations of factors with a crucial role in inflammation and angiogenesis were measured in CSF via ELISA testing (pg/ml): Angiopoietin 2, VEGF-A and C, RANTES, IL 1 beta and IL 8. Additionally, evaluated the status of the blood-spinal cord barrier (BSCB) by Reibers´diagnostic in all participants. Groups evidently differed in their neurological status (mJOA: DCM 10.1 ± 3.3, TAAA 17.3 ± 1.2, p < .001; NDI: DCM 47.4 ± 19.7, TAAA 5.3 ± 8.6, p < .001). There were no particular differences in age and gender distribution. However, we detected statistically significant differences in concentrations of mediators between the groups: Angiopoietin 2 (DCM 267.1.4 ± 81.9, TAAA 408.6 ± 177.1, p < .001) and VEGF C (DCM 152.2 ± 96.1, TAAA 222.4 ± 140.3, p = .04). DCM patients presented a mild to moderate BSCB disruption, controls had no signs of impairment. In patients with DCM, we measured decreased concentrations of angiogenic mediators. These results correspond to findings of immune mediated secondary harm in acute spinal cord injury. Reduced angiogenic activity could be a relevant part of the pathogenesis of DCM and secondary harm to the spinal cord.

Liquid and Droplet Transport in Brush-Coated Cylindrical Nanochannels: Brush-Assisted Droplet Formation

We study, by coarse-grained molecular dynamics simulations, equilibrium and flow properties of a liquid in cylindrical nanochannels, coated with polymer brushes. The parameters of the interaction potential model confer a chemical incompatibility between brush monomers and liquid particles. First, we study cylindrical channels whose radii are larger than the brush height and a continuous column of liquid forms at the center of the channel. These results are contrasted to the limiting case in which the radius of the cylinder is comparable to the brush height. In this second case, the grafted polymers interact across the channel and "close" it. We observe a train of droplets as the stable liquid morphology. The droplet size is comparable to the cylinder radius. By applying a constant body force onto the liquid, we induce a Poiseuille-like flow and investigate the morphology and flow rate as a function of driving force. Upon increasing the driving force, we encounter a nonequilibrium transition from a closed channel with slowly moving droplets to a flowing liquid thread at the center. The switching between these two states is reversible.

Defects and plasticity in ultrastrong supercrystalline nanocomposites

Supercrystalline nanocomposites are nanoarchitected materials with a growing range of applications but unexplored in their structural behavior. They typically consist of organically functionalized inorganic nanoparticles arranged into periodic structures analogous to crystalline lattices, including superlattice imperfections induced by processing or mechanical loading. Although featuring a variety of promising functional properties, their lack of mechanical robustness and unknown deformation mechanisms hamper their implementation into devices. We show that supercrystalline materials react to indentation with the same deformation patterns encountered in single crystals. Supercrystals accommodate plastic deformation in the form of pile-ups, dislocations, and slip bands. These phenomena occur, at least partially, also after cross-linking of the organic ligands, which leads to a multifold strengthening of the nanocomposites. The classic shear theories of crystalline materials are found to describe well the behavior of supercrystalline nanocomposites, which result to feature an elastoplastic behavior, accompanied by compaction.

[External fixation for treatment of peripartum pubic symphysis separation : Clinical case and discussion]

A complete peripartum pubic symphysis separation is a rare but severe complication of natural birth. Its incidence is estimated to be 0.03-3 ‰. Minor partial separations with a small width can be treated with a pelvic binder. Separations with major dehiscence should be treated by surgical reduction and fixation. This article presents the case of a 30-year-old woman who suffered a complete rupture of the pubic symphysis during the birth of her second child. Radiographic dehiscence was 39 mm. The operative treatment was carried out using a supra-acetabular external fixator for 12 weeks with a good result.

Predicting zebrafish spatial avoidance triggered by discharges of dairy wastewater: An experimental approach based on self-purification in a model river

Wastewater discharges from dairy industries can cause a range of harmful effects in aquatic ecosystems, including a decline in biodiversity due to species evasion. Therefore, it is important to know the purification potential of rivers for the removal of pollutants released in dairy wastewater (DWW). The hypothesis adopted in this work was that the release of DWW into stretches of the Ribeirão dos Pombos River (São Paulo State, Brazil) might trigger an avoidance response, resulting in fish migrating to other regions, with the response being greater when the self-cleaning potential of the river is smaller. Therefore, the goals of the present study were to: (i) investigate how land use and seasonality of the rainfall regime influence the quality of the water in different areas of the river (P1: river source; P2: urban region; P3: rural region); (ii) assess the potential of the river to purify DWW; and (iii) evaluate the potential toxicity and repellency of DWW to the freshwater fish Danio rerio, using acute toxicity (mortality) and non-forced avoidance tests, respectively. P1 was shown to be the most preserved area. The chemical composition of the river varied seasonally, with higher concentrations of Cl^- and SO₄^2- at P3 during the rainy period. The river purification potential for DWW was higher at P2, due to greater microbiological activity (associated with higher BOD). The DWW was more acutely toxic in water from P2. The avoidance response was strongly determined by the concentration of DWW, especially for water from P2. The high capacity for self-cleaning at P2 did not seem sufficient to maintain the stability of the ecosystem. Finally, the non-forced exposure system proved to be a suitable approach that can assist in predicting how contaminants may affect the spatial distributions of organisms.

[Bed capacity management in times of the COVID-19 pandemic : A simulation-based prognosis of normal and intensive care beds using the descriptive data of the University Hospital Augsburg]

BACKGROUND

Following the regional outbreak in China, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has spread all over the world, presenting the healthcare systems with huge challenges worldwide. In Germany the coronavirus diseases 2019 (COVID-19) pandemic has resulted in a slowly growing demand for health care with a sudden occurrence of regional hotspots. This leads to an unpredictable situation for many hospitals, leaving the question of how many bed resources are needed to cope with the surge of COVID-19 patients.

OBJECTIVE

In this study we created a simulation-based prognostic tool that provides the management of the University Hospital of Augsburg and the civil protection services with the necessary information to plan and guide the disaster response to the ongoing pandemic. Especially the number of beds needed on isolation wards and intensive care units (ICU) are the biggest concerns. The focus should lie not only on the confirmed cases as the patients with suspected COVID-19 are in need of the same resources.

MATERIAL AND METHODS

For the input we used the latest information provided by governmental institutions about the spreading of the disease, with a special focus on the growth rate of the cumulative number of cases. Due to the dynamics of the current situation, these data can be highly variable. To minimize the influence of this variance, we designed distribution functions for the parameters growth rate, length of stay in hospital and the proportion of infected people who need to be hospitalized in our area of responsibility. Using this input, we started a Monte Carlo simulation with 10,000 runs to predict the range of the number of hospital beds needed within the coming days and compared it with the available resources.

RESULTS

Since 2 February 2020 a total of 306 patients were treated with suspected or confirmed COVID-19 at this university hospital. Of these 84 needed treatment on the ICU. With the help of several simulation-based forecasts, the required ICU and normal bed capacity at Augsburg University Hospital and the Augsburg ambulance service in the period from 28 March 2020 to 8 June 2020 could be predicted with a high degree of reliability. Simulations that were run before the impact of the restrictions in daily life showed that we would have run out of ICU bed capacity within approximately 1 month.

CONCLUSION

Our simulation-based prognosis of the health care capacities needed helps the management of the hospital and the civil protection service to make reasonable decisions and adapt the disaster response to the realistic needs. At the same time the forecasts create the possibility to plan the strategic response days and weeks in advance. The tool presented in this study is, as far as we know, the only one accounting not only for confirmed COVID-19 cases but also for suspected COVID-19 patients. Additionally, the few input parameters used are easy to access and can be easily adapted to other healthcare systems.

X-ray Zernike phase contrast tomography: 3D ROI visualization of mm-sized mice organ tissues down to sub-cellular components

Thanks to its non-invasive nature, X-ray phase contrast tomography is a very versatile imaging tool for biomedical studies. In contrast, histology is a well-established method, though having its limitations: it requires extensive sample preparation and it is quite time consuming. Therefore, the development of nano-imaging techniques for studying anatomic details at the cellular level is gaining more and more importance. In this article, full field transmission X-ray nanotomography is used in combination with Zernike phase contrast to image millimeter sized unstained tissue samples at high spatial resolution. The regions of interest (ROI) scans of different tissues were obtained from mouse kidney, spleen and mammalian carcinoma. Thanks to the relatively large field of view and effective pixel sizes down to 36 nm, this 3D approach enabled the visualization of the specific morphology of each tissue type without staining or complex sample preparation. As a proof of concept technique, we show that the high-quality images even permitted the 3D segmentation of multiple structures down to a sub-cellular level. Using stitching techniques, volumes larger than the field of view are accessible. This method can lead to a deeper understanding of the organs' nano-anatomy, filling the resolution gap between histology and transmission electron microscopy.

Retraction notice to "Changes in regulators of the circulation in patients undergoing lung surgery" [Br J Anaesth 79 (1997) 733-9]

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). This article has been retracted at the request of the Editor-in-Chief, Professor Hugh Hemmings, based on the recommendations of Justus-Liebig-University Giessen following an internal review of research conducted by Joachim Boldt at the University. This is further described in 'Further Retractions of Articles by Joachim Boldt', https://doi.org/10.1016/j.bja.2020.02.024.

Using Uniaxial Stress to Probe the Relationship between Competing Superconducting States in a Cuprate with Spin-stripe Order

We report muon spin rotation and magnetic susceptibility experiments on in-plane stress effects on the static spin-stripe order and superconductivity in the cuprate system La_{2-x}Ba_{x}CuO_{4} with x=0.115. An extremely low uniaxial stress of ∼0.1  GPa induces a substantial decrease in the magnetic volume fraction and a dramatic rise in the onset of 3D superconductivity, from ∼10 to 32 K; however, the onset of at-least-2D superconductivity is much less sensitive to stress. These results show not only that large-volume-fraction spin-stripe order is anticorrelated with 3D superconducting coherence but also that these states are energetically very finely balanced. Moreover, the onset temperatures of 3D superconductivity and spin-stripe order are very similar in the large stress regime. These results strongly suggest a similar pairing mechanism for spin-stripe order and the spatially modulated 2D and uniform 3D superconducting orders, imposing an important constraint on theoretical models.

Intake, digestibility, ingestive behavior, production, and composition of goat milk supplemented with detoxified castor bean meal added urea as a replacement of soybean meal

This study evaluated the castor bean meal detoxified with calcium hydroxide [Ca(OH)2] added urea replacing soybean meal in the diet of lactating goats from milk production and composition, intake, digestibility, and ingestive behavior. Eight Alpine multiparous goats weighting 44.3 ± 5.3 kg and at approximately 60 days of lactation were confined and randomly distributed in 4 × 4 double Latin squares, with four inclusion levels of detoxified castor meal: control (0), 25, 50, and 75 g/kg dry matter (DM) total. Detoxified castor bean meal replacing soybean meal (P > 0.05) in goats diet did not affect intake and digestibility of DM, crude protein, ether extract, neutral detergent fiber (NDF), total carbohydrates, non-fibrous carbohydrates and total digestible nutrients, times spent for eating, and efficiency ratios of rumination and eating. However, the times spent for rumination and idling showed a quadratic trend decrease (P < 0.01) from the level of 50.0-g/kg DM. The milk production, and the milk production correction showed a quadratic trend increase and feeding efficiency a quadratic decrease (P = 0.03) due inclusion of detoxified castor bean meal replacing soybean meal up to the level of 25.0 g/kg. The fat, protein, lactose, total solids, nonfat solids, and milk urea nitrogen content (g/day) presented a quadratic increase (P < 0.05) by detoxified castor meal inclusion. Detoxified castor bean meal added urea in the Alpine goats diet could be included up to the 25.0 g/kg level replacing soybean meal in the diet because improve milk production and composition and feeding efficiency of goats without negatively effect on intake, digestibility and ingestive behavior.

Panton-Valentine leukocidin-positive Staphylococcus aureus in skin and soft tissue infections from primary care patients

OBJECTIVES

To characterize deep skin and soft tissue infections (dSSTI) caused by Panton-Valentine leukocidin (PVL)-positive versus PVL-negative Staphylococcus aureus isolates.

METHODS

We performed a retrospective analysis of patients' records including S. aureus isolates from outpatients with dSSTI. Samples had been submitted by primary care physicians, i.e. general practitioners, surgeons, dermatologists and paediatricians, located in Berlin, Germany, in 2007-2017. Bacterial isolates were identified and tested for antimicrobial susceptibility by VITEK 2; PVL was detected by PCR.

RESULTS

In total, 1199 S. aureus isolates from 1074 patients with dSSTI were identified, and 613 (51.1%) of 1199 samples were PVL⁺. The median age of patients with PVL⁺S. aureus was lower than in patients with PVL- S. aureus (34 years, range 0-88 years, vs. 44 years, range 0-98 years; p < 0.0001). PVL was associated with repeated/multiple samples compared to single sample submission (69/92, 75% vs. 448/982, 45.6%, p < 0.0001; odds ratio (OR), 3.6; 95% confidence interval (CI), 2.2-5.8). Interestingly, the highest PVL positivity rate was found in isolates from gluteal (82/108, 75.9%; OR, 3.6; 95% CI, 2-5) or axillary (76/123, 61.8%; OR, 2; 95% CI, 1.1-3.3) localizations compared to isolates from the arm. The PVL positivity rate did not increase over time. Yet we noticed an increase in the trimethoprim/sulfamethoxazole (SXT) resistance rate in PVL⁺ isolates, mainly methicillin-sensitive S. aureus, when considering SXT resistance rates of 2007-2012 versus 2013-2017 (35/226, 15.5% vs. 74/289, 25.6%; p 0.01).

CONCLUSIONS

In outpatients, gluteal and axillary dSSTI are indicative of PVL⁺S. aureus. Providing SXT as a complementary treatment for dSSTI should be based on susceptibility testing.

[Current treatment strategies for lower leg fractures in adults]

Shaft fractures of the tibia and fibula mainly affect younger patients and are therefore of great socioeconomic importance. Due to the high proportion of high-energy direct trauma mechanisms and the thin soft tissue covering layer of the ventromedian tibia, open factures occur in up to 39%. A structured diagnostic and therapeutic approach is essential for successful treatment. Reamed intramedullary nailing is currently the gold standard surgical procedure. The suprapatellar approach, representing an interesting alternative to the popular infrapatellar approach, postoperative complications, such as anterior knee pain as well as the management of non-unions are discussed in this article. Furthermore, the indications and the application of minimally invasive plate osteosynthesis (MIPO) and external fixators are described. Every trauma surgeon should be familiar with the etiology and the surgical treatment of compartment syndrome. A firm knowledge of the classifications of open and closed soft tissue injury is mandatory.

Observation of the Spin-Orbit Gap in Bilayer Graphene by One-Dimensional Ballistic Transport

We report on measurements of quantized conductance in gate-defined quantum point contacts in bilayer graphene that allow the observation of subband splittings due to spin-orbit coupling. The size of this splitting can be tuned from 40 to 80  μeV by the displacement field. We assign this gate-tunable subband splitting to a gap induced by spin-orbit coupling of Kane-Mele type, enhanced by proximity effects due to the substrate. We show that this spin-orbit coupling gives rise to a complex pattern in low perpendicular magnetic fields, increasing the Zeeman splitting in one valley and suppressing it in the other one. In addition, we observe a spin polarized channel of 6e^{2}/h at high in-plane magnetic field and signatures of interaction effects at the crossings of spin-split subbands of opposite spins at finite magnetic field.